Improper voltage detection for electronic circuit breaker

ABSTRACT

A method of tripping a circuit breaker including sampling an AC line voltage at regular intervals during a first time period to generate a plurality of AC line voltage samples. Each sample of the set of AC line voltage samples is summed to generate a voltage area value. A controller determines whether the voltage area value exceeds a threshold. In response to the voltage area value exceeding the threshold, an amount determined as a function of the voltage area value is added to a count value. The circuit breaker is caused to trip in response to the count value equaling or exceeding a maximum count value. 
     An improper line-to-neutral voltage can be detected by monitoring the line-to-neutral voltage and comparing it to a function such as a trip curve. Thus, components downstream from a circuit breaker, as well as the circuit breaker itself, can be protected from prolonged exposure to improper voltages, which can lead to component failure.

FIELD OF THE INVENTION

The present invention relates to detecting improper voltage conditionsin electronic circuit breakers.

BACKGROUND OF THE INVENTION

A typical two-pole circuit breaker (for example, a residential two-polecircuit breaker) receives as inputs two line voltages and a neutralvoltage. The two line voltages (line-to-neutral voltages) typically are120V alternating current (“AC”) signals, 180 degrees out of phase fromone another. Each line voltage alternates in polarity with respect tothe neutral voltage, which is determined from the two line voltages in aconventional manner. The sum of the two line voltages (the line-to-linevoltage) is a 240V AC voltage.

A microprocessor or controller in the circuit breaker can be used tomeasure line voltages. For example, circuits can be used to divide aline voltage and output the divided signal to the microprocessor. Themicroprocessor includes an analog to digital (A/D) converter to receivethe analog voltage and convert it to a digital voltage for measurementby the microprocessor.

Basic AC voltage power quality is expected throughout a system employinga circuit breaker. Due to variations in the distribution networkupstream from the circuit breaker, the AC voltage is expected to varywithin a certain range. Variations in the AC voltage outside of thisrange could damage the circuit breaker or components (such asappliances) downstream from the circuit breaker. For example, metaloxide varistors (MOVs) in many components will heat up when subjected toa prolonged overvoltage and eventually fail. Other downstream componentscan similarly fail if subjected to prolonged overvoltage conditions.Likewise, circuit breakers often include MOVs or other components thatcan fail if subjected to a prolonged overvoltage condition.

Currently, circuit breakers are tripped based on measurements of currentrather than voltage. A gradual increase in voltage will not cause thesecircuit breakers to trip. What is needed is a way to detect suchimproper voltage conditions by monitoring a line-to-neutral voltageand/or a line-to-line voltage and take appropriate action to limit theeffect of improper voltages on the circuit breaker and downstreamcomponents.

SUMMARY OF THE INVENTION

According to an aspect of the present disclosure, a method of tripping acircuit breaker includes sampling an AC line voltage at regularintervals during a first time period to generate a plurality of AC linevoltage samples. Each sample of the set of AC line voltage samples issummed to generate a voltage area value. A controller determines whetherthe voltage area value exceeds a threshold. In response to the voltagearea value exceeding the threshold, an amount determined as a functionof the voltage area value is added to a count value. The circuit breakeris caused to trip in response to the count value equaling or exceeding amaximum count value.

According to another aspect of the present disclosure, a circuit breakerincludes a first circuit configured to receive an alternating current(AC) line voltage and generate a signal indicative of the AC linevoltage. The circuit breaker also includes a controller coupled to thefirst circuit configured to sample the AC line voltage at regularintervals during a first time period to generate a plurality of AC linevoltage samples and sum each sample of the set of AC line voltagesamples to generate a voltage area value. The controller is configuredto determine whether the voltage area value exceeds a threshold. Inresponse to the voltage area value exceeding the threshold, thecontroller is configured to add to a count value an amount determined asa function of the voltage area value, and cause a circuit breaker totrip in response to the count value equaling or exceeding a maximumcount value.

According to another aspect of the present disclosure, in a circuitbreaker, a method includes summing a plurality of samples of analternating current (AC) voltage to generate a voltage area value. Ifthe voltage area value indicates that the AC voltage is an anomalousvoltage, a circuit breaker is caused to trip.

Advantageously, components downstream from a circuit breaker, as well asthe circuit breaker itself, can be protected from prolonged exposure toimproper voltages, which can lead to component failure. For example, bydetecting an overvoltage condition and tripping the circuit breaker upondetection of the overvoltage condition, the circuit breaker anddownstream components can be protected from overheating due to theovervoltage condition.

The foregoing and additional aspects and embodiments of the presentinvention will be apparent to those of ordinary skill in the art in viewof the detailed description of various embodiments and/or aspects, whichis made with reference to the drawings, a brief description of which isprovided next.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings.

FIG. 1A is a circuit diagram of a system that includes some of theelements used in aspects of the present disclosure, including circuitryfor measuring a line-to-line voltage and a line-to-neutral voltage anddetermining another line-to-neutral voltage, wherein a second circuitand a fourth circuit share at least one resistor;

FIG. 1B is a flow chart of a method that includes some of the aspects ofthe present disclosure;

FIG. 2 is a circuit diagram of a system that includes some of theelements used in aspects of the present disclosure, including circuitryfor measuring a line-to-line voltage and a line-to-neutral voltage anddetermining another line-to-neutral voltage, wherein a second circuitand a fourth circuit share at least one resistor and wherein a secondcircuit and a third circuit share at least one resistor;

FIG. 3 is a circuit diagram of a system that includes some of theelements used in aspects of the present disclosure, including circuitryfor measuring a line-to-line voltage and a line-to-neutral voltage anddetermining another line-to-neutral voltage, wherein first, second,third, and fourth circuits do not share resistors, and wherein thefourth circuit is connected to first and second line inputs;

FIG. 4 is a circuit diagram of a system that includes some of theelements used in aspects of the present disclosure, including circuitryfor measuring a line-to-line voltage and a line-to-neutral voltage anddetermining another line-to-neutral voltage, wherein first, second,third, and fourth circuits do not share resistors, and wherein thefourth circuit is connected to a neutral input;

FIG. 5 is a circuit diagram of a system that includes some of theelements used in aspects of the present disclosure, including circuitryfor measuring two line-to-neutral voltages and determining aline-to-line voltage, wherein first and second circuits are connectedbetween line inputs and analog reference, respectively;

FIG. 6 is a circuit diagram of a system that includes some of theelements used in aspects of the present disclosure, including circuitryfor measuring two line-to-neutral voltages and determining aline-to-line voltage, wherein first and second circuits are connectedbetween line inputs and a neutral input, respectively;

FIG. 7 is a circuit diagram of a system that includes some of theelements used in aspects of the present disclosure, including circuitryfor measuring a line-to-line voltage and a line-to-neutral voltage anddetermining another line-to-neutral voltage without a circuit todetermine polarity;

FIG. 8 is a flow chart of a method of detecting an improper voltage thatincludes some of the elements used in aspects of the present disclosure;and

FIG. 9 is a graph of trip curves that includes some of the elements usedin aspects of the present disclosure.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Although the invention will be described in connection with certainaspects and/or embodiments, it will be understood that the invention isnot limited to those particular aspects and/or embodiments. On thecontrary, the invention is intended to cover all alternatives,modifications, and equivalent arrangements as may be included within thespirit and scope of the invention as defined by the appended claims.

FIG. 1A is a simplified circuit diagram illustrating aspects of thepresent invention, including circuitry for measuring a line-to-linevoltage and a line-to-neutral voltage and determining anotherline-to-neutral voltage. A two pole circuit breaker 100 includes twoline inputs L1 and L2 (110, 114) to receive AC input voltages (e.g.,120V AC line to neutral) through line-powered trip solenoids 112, 116,respectively, for tripping the circuit breaker 100. The circuit breakerincludes an additional line input, i.e., a neutral input 118. Each ofthe two line voltages alternates in polarity with respect to the neutralinput 118. The line voltages are 180 degrees out of phase from oneanother. The line-to-line voltage, or voltage difference between the twoline inputs 110, 114, is a 240V AC voltage.

A full-wave diode bridge 120 and rectifying diodes 122 and 124 togetherrectify the voltages at line inputs 110, 114. The line voltage ofpositive polarity is permitted to pass through the full-wave diodebridge 120 and rectifying diodes 122, 124, while ground is pulled towardthe voltage of the line input of negative polarity. The half cycle ofpositive polarity is input to a voltage regulator 126, which outputs aregulated voltage.

The circuit breaker 100 includes a first circuit 128 for measuring thevoltage difference between the two line inputs 110, 114. The firstcircuit 128 includes a resistor 132, connected to the line input 110 andthe resistor 134, connected to the line input 114. The resistors 132,133, and 134 form voltage dividers between the line inputs 110, 114 andground. The node 130, between the resistors 132, 133, and 134, isconnected to a controller such as a microprocessor 136. A person ofordinary skill in the art will recognize that a variety of controllerscould be used in place of a microprocessor, for example an applicationspecific integrated circuits (ASIC), field programmable gate array(FPGA), etc. The resistors 132, 133 and 134 are configured to divide theline-to-line voltage to produce at the node 130 a voltage range that canbe accepted by the microprocessor 136. For example, if the line voltageat line inputs 110 and 114 are 120V AC, the resistor 132 may be 998 kΩ,the resistor 133 may be 7.5 kΩ, and the resistor 134 may be 998 kΩ. Thevoltage at the node 130 represents the voltage difference between theline inputs 110 and 114. The microprocessor 136 includes an A/Dconverter (not shown) to receive the analog voltage from the node 130 atan analog input 138 and to convert it into a digital representationusable by the microprocessor 136 by sampling the voltage at the node 130at regular intervals.

The circuit breaker 100 also includes a second circuit 129 for measuringthe voltage difference between the neutral input 118 and whichever ofthe two line inputs 110, 114 is of negative polarity. The second circuit129 includes resistors 142, 144, and 146, which form a voltage dividerbetween the neutral input 118 and ground. The node 140 is betweenresistor 146 and the combined resistance of resistors 142 and 144. Thevoltage at the node 140 is a divided representation of the voltagedifference between the voltage at the neutral input 118 and ground.Resistors 142, 144, and 146 are configured to divide the line-to-neutralvoltage to produce at the node 140 a voltage range that can be acceptedby the microprocessor 136. For example, if the line voltage at lineinputs 110 and 114 are 120V AC, the resistor 142 may be 309 kΩ, theresistor 144 may be 196 kΩ, and the resistor 146 may be 5.9 kΩ. Becausethe line voltage that is at a negative polarity serves as ground, thevoltage at node 140 represents the voltage difference between theneutral input 118 and whichever of the two line inputs 110, 114 is ofnegative polarity. For example, during the half-cycle that the lineinput 110 is of negative polarity with respect to the neutral line input118, the voltage at node 140 represents the voltage difference betweenthe neutral input 118 and line input 110. The node 140 is connected tothe microprocessor 136, which includes the A/D converter to receive theanalog voltage from node 140 at analog input 148 and convert it into adigital representation usable by the microprocessor 136 by sampling thevoltage at node 140 at regular intervals.

The circuit breaker 100 also includes a third circuit 150 to indicatewhich of the line inputs 110, 114 is at a positive polarity. The thirdcircuit 150 includes resistors 154 and 156 connected between the lineinput 114 and ground. The resistors 154 and 156 form a voltage divider.A node 152 is between resistors 154 and 156 and is connected tomicroprocessor 136. The resistors 154 and 156 are configured to dividethe voltage at line input 114 to a voltage range at the node 152 thatcan be accepted by the microprocessor 136 at a digital input 153 withoutthe use of an A/D converter and can be interpreted as a logic signal.For example, for a line input voltage of 120V AC at line input 114, theresistor 154 can be 974 kΩ and the resistor 156 can be 130 kΩ. Thevoltage at the node 152 represents the polarity of the voltage at theline input 114. If the voltage at the line input 114 is of negativepolarity, the line input 114 serves as ground. Thus, the line input 114and ground are at substantially the same potential (e.g., a diode dropaway from each other), and the voltage at node 152 is zero, representinga logic value of zero. If the voltage at the line input 114 is of apositive polarity, the line input 110 (at a negative polarity) serves asground, and there is a positive potential between the line input 114 andground, and the node 152 is at a positive potential, representing alogic value of one. The microprocessor 136 interprets a logic value ofzero at the node 152 to indicate that the line input 114 is at anegative polarity and the line input 110 is at a positive polarity.Likewise, the microprocessor 136 interprets a logic value of one at thenode 152 to indicate that the line input 114 is at a positive polarityand the line input 110 is at a negative polarity.

The circuit breaker 100 can also optionally include a fourth circuit 160to indicate when the voltage at the line input 110 or the line input 114is equal to the voltage at the neutral input 118. If the AC linevoltages at the line inputs 110 and 114 are 180 degrees out of phase,their respective voltages will be equal to the voltage at the neutralinput 118 at the same time (e.g., at phase angles of zero degrees, 180degrees, etc.). A point at which the voltage at a line input is equal tothe voltage at the neutral input 118 can be referred to as azero-crossing point. This also represents the point at which the voltageat that line input changes polarity (i.e., from positive a polarity to anegative polarity, or from a negative polarity to a positive polarity).The fourth circuit 160 includes three resistors 142, 164, and 166, whichform a voltage divider between the neutral input 118 and ground. A node162 is between the resistor 166 and the combined resistance of theresistors 142 and 164. The node 162 is connected to the microprocessor136. The resistors 142, 164, and 166 are configured to divide thevoltage between the neutral input 118 and ground to produce at the node162 a voltage range that can be accepted by the microprocessor 136 at adigital input 163 without the use of an A/D converter and can beinterpreted as a logic signal. For example, the resistor 142 may be 309kΩ, the resistor 164 may be 196 kΩ, and the resistor 166 may be 130 kΩ.

As stated above, whichever line input 110, 114 is of negative polarityserves as ground. At a point where the voltages at the line inputs 110and 114 are changing polarity (this will be the same point in time forboth inputs when the voltages at the line inputs 110 and 114 are 180degrees out of phase) ground will be equal to both line inputs 110, 114,and the neutral input 118. Thus, at a zero-crossing point, the neutralinput 118 will be at ground, and there will be no difference inpotential between the neutral input 118 and ground. Accordingly, thevoltage at the node 162 will be zero, which represents a logic value ofzero. When the line voltages are not at a zero-crossing point, theneutral input 118 will be at a higher potential than ground (which issubstantially (e.g., about a diode drop) equal to the line input 110,114 of negative polarity). Thus, the voltage at the node 162 will be apositive value, which represents a logic value of one. Themicroprocessor 136 interprets a logic value of zero at the node 162 toindicate that the line inputs 110, 114 are at a zero-crossing point.Likewise, the microprocessor 136 interprets a logic value of one at thenode 152 to indicate that the line inputs 110, 114 are not at azero-crossing point.

FIG. 1B is a flow chart illustrating a method that implements thecircuits described above. The first circuit 128 outputs a first analogsignal at the node 130 representing the line-to-line voltage (voltagedifference between the line inputs 110 and 114) (170). This representsthe instantaneous voltage of the 240V AC voltage. The A/D converter atthe microprocessor 136 converts the first analog signal to a firstdigital value (172). The microprocessor 136 samples the first digitalvalue (174). The microprocessor 136 is programmed to determine aline-to-line voltage measurement from the first digital value (176), forexample by comparing the first digital value to a set of stored values,or by executing a function defining a relationship between the possibledigital values and corresponding line-to-line voltage measurements, asis known in the art. The microprocessor 136 can store this value for usein calculations.

The second circuit 129 outputs a second analog signal at the node 140representing the line-to-neutral voltage (the voltage difference betweenthe neutral input 118 and the line input of 110 and 114 of a negativepolarity ) (178). This represents the instantaneous voltage differencebetween the neutral line input 118 and whichever of the two line inputs110 and 114 is of negative polarity at that time. The A/D converter atthe microprocessor 136 converts the second analog signal to a seconddigital value (180). The microprocessor 136 samples the second digitalvalue (182). The microprocessor 136 is programmed to determine theline-to-neutral voltage measurement from the second digital value (184),similarly to how it determines the line-to-line voltage from the firstdigital value. The microprocessor 136 can store this value for use incalculations.

The third circuit 150 outputs a polarity signal at node 152 representingthe polarity of the second line voltage (186). The microprocessor 136samples the polarity signal and interprets it as a logic signalidentifying the line input of 110 and 114 of a negative polarity (188).As explained above, if the line input 114 is of a negative polarity, thevoltage at the node 150 will be zero; if the line input 114 is of apositive polarity, the voltage at the node 150 will be a positive value.The microprocessor 136 assigns the second digital value (representingthe line-to-neutral voltage measurement) to the line input of negativepolarity (190). For example, if the line input 114 is of a negativepolarity, the voltage at the node 150 will be zero. The microprocessor136 can interpret the voltage value of zero as a logic zero, and assignthe second digital value to the line input 114. If the line input 114 isof a positive polarity, the voltage at the node 150 will be a positivevalue. The microprocessor 136 can interpret the positive voltage valueas a logic one, and assign the second digital value to the line input110. The microprocessor 136 can sample and process the first and secondanalog signals and the polarity signal simultaneously, consecutively, orin any order.

The microprocessor 136 is programmed to calculate a value for theline-to-neutral voltage of the line input of positive polarity from theline-to-line voltage measurement and the line-to-neutral voltagemeasurement of the line input of negative polarity. For example, themicroprocessor 136 can be programmed to subtract the first digital valuefrom the second digital value to calculate a voltage value of the lineinput of a positive polarity (192). The microprocessor 136 can includean arithmetic logic unit (ALU) to perform such calculations. Themicroprocessor 136 assigns this calculated voltage value to the lineinput of 110 and 114 of a positive polarity (194). For example, if thepolarity signal is interpreted as a logic zero, the microprocessor 136assigns the calculated voltage value to the line input 110; if thepolarity signal is interpreted as a logic one, the microprocessor 136assigns the calculated voltage value to the line input 114.

As explained above, the circuit breaker 100 may also include the fourthcircuit 160. The fourth circuit 160 outputs a zero-crossing signal atnode 162 indicating that the voltage of one (or both) of the line inputs110, 114 equals the voltage of the neutral input 118 (196). Themicroprocessor 136 interprets the zero-crossing signal as a logic signalidentifying a zero-crossing point (198). A zero-crossing point can beused by the microprocessor 136 as a timing reference. For example, themicroprocessor 136 can be configured to sample a predetermined number ofsamples of the first and second analog signals and the polarity signalbeginning when the zero-crossing signal indicates a zero-crossing point.

The polarity signal may also be used to correlate the phase of thecurrent at each line input with the full wave rectified amplitude of thevoltage. For example, a current monitoring circuit for each of the lineinputs 110, 114 can be coupled to the microprocessor 136 at currentmonitoring inputs. The current monitoring circuits include DC offsets.By determining that the current at a current monitoring input is aboveor below the DC offset, the microprocessor can determine whether thecurrent is of a positive or negative phase. This phase information canbe compared to the polarity signal. If the phase information from thecurrent monitoring input does not match the polarity signal, the linesignal conductors inside the circuit breaker may be improperly connected(e.g., the line intended to be connected to line input 110 is connectedto line input 114 and vise versa).

The voltage information can also be used by the microprocessor toidentify problems with the voltage inputs, such as the loss of one ofthe line voltages (sometimes referred to as loss of phase), loss of theneutral input, loss of phase of the line voltages, etc. The voltage andcurrent information could also be used by the microprocessor todetermine information about the load on the circuit, such as how muchpower the load is consuming, or for use in the detection of arcingfaults.

Microprocessors typically have a limited number of analog inputsconnected to the microprocessor's A/D converter. If more analog inputsare required that the microprocessor has, it could be necessary to use alarger and more expensive microprocessor that has a larger number ofanalog inputs. In this embodiment, three voltages, i.e., the twoline-to-neutral voltages and the line-to-line voltage, can be measuredusing only two analog inputs. Moreover, as can be seen, bothline-to-neutral voltages and the line-to-line voltage can be measuredusing fewer circuit components, and specifically fewer high-voltagecircuit components, saving space on a PCBA. This also reduces the numberof high voltage parallel traces, which can reduce PCBA spacingrequirements. Calculating a line-to-neutral voltage rather than samplingit using an A/D converter can also save computational time, asperforming the calculation can take fewer microprocessor resources thanperforming an A/D conversion.

In this embodiment, the fourth circuit 160 and the second circuit 129share at least one component, the resistor 142. Sharing components amongthe circuits can further reduce the number of components on the PCBA andcan simplify layout of the circuitry on the PCBA.

FIG. 2 is a simplified circuit diagram illustrating aspects of thepresent invention, including circuitry for measuring a line-to-linevoltage and a line-to-neutral voltage and determining anotherline-to-neutral voltage. As with FIG. 1A, above, a two pole circuitbreaker 200 includes two line inputs L1 and L2 (110, 114) to receive ACinput voltages (e.g., 120V AC) through line-powered trip solenoids 112,116, respectively, and neutral input 118. The full-wave diode bridge 120and the rectifying diodes 122 and 124 rectify the voltages at the lineinputs 110, 114. The half cycle of positive polarity is input to thevoltage regulator 126, which outputs a regulated voltage.

The circuit breaker 200 includes a first circuit 202 for measuring thevoltage difference between the line inputs 110, 114. The first circuit202 includes a resistor 212, connected to the line input 110, tworesistors 214 and 216 connected in series to the line input 114, and aresistor 218 connected between the resistors 212 and 216 and ground. Theresistor 212, the combination of the resistors 214, 216, and resistor218 form voltage dividers between the line inputs 110, 114 and ground. Anode 210, between the three resistors 212, 216, and 218 is connected tothe microprocessor 136. The resistors 212, 214, 216, and 218 areconfigured to divide the line-to-line voltage to produce at the node 210a range that can be accepted by the microprocessor 136. The voltage atthe node 210 represents the voltage difference between the line inputs110 and 114. The microprocessor 136 includes the A/D converter (notshown) to receive the analog voltage from the node 210 at the analoginput 138 and convert it into a digital representation usable by themicroprocessor 136 by sampling the voltage at the node 210 at regularintervals.

The circuit breaker 200 also includes a second circuit 204 for measuringthe voltage difference between the neutral input 118 and whichever ofthe two line inputs 110, 114 is of negative polarity. The second circuit204 includes three resistors 222, 224, and 226, which form a voltagedivider between the neutral input 118 and ground. A node 220 is betweenthe resistor 226 and the combined resistance of the resistors 222 and224. The voltage at the node 220 is a divided down version of, andrepresents, the voltage difference between the voltage at the neutralinput 118 and ground. The resistors 222, 224, and 226 are configured todivide the line-to-neutral voltage to produce at the node 220 a rangethat can be accepted by the microprocessor 136. The voltage at the node220 represents the voltage difference between the neutral input 118 andwhichever of the two line inputs 110, 114 is of a negative polarity. Thenode 220 is connected to the microprocessor 136, which includes the A/Dconverter to receive the analog voltage from the node 220 at the analoginput 148 and convert it into a digital representation usable by themicroprocessor 136 by sampling the voltage at the node 220 at regularintervals.

The circuit breaker 200 also includes a third circuit 206 to indicatewhich of the line inputs 110, 114 is at a negative polarity (and whichis at a positive polarity, as the other line input will be of oppositepolarity when the line voltages are 180 degrees out of phase). The thirdcircuit 206 includes three resistors 214, 232, and 234 connected betweenthe line input 114 and ground. The resistor 234 and the combination ofthe resistors 214 and 232 form a voltage divider. A node 230 is betweenthe resistors 232 and 234, and is connected to the microprocessor 136 atthe digital input 153. The resistors 214, 232, and 234 are configured todivide the voltage difference between the line input 114 and ground andproduce at the node 230 a voltage range that can be accepted by themicroprocessor 136 without the use of an A/D converter and can beinterpreted as a logic signal. The voltage at the node 230 representsthe polarity of the voltage at the line input 114. If the voltage at theline input 114 is of a negative polarity, the voltage at the node 230will be zero, representing a logic value of zero; if the voltage at theline input 114 is of a positive polarity, the node 230 will be at apositive potential, representing a logic value of one. Themicroprocessor 136 interprets a logic value at the node 230 to indicatethat the line input 114 is at a negative polarity and the line input 110is at a positive polarity (for logic value of zero) or vice versa (forlogic value of one).

The circuit breaker 200 may also include a fourth circuit 208 toindicate a zero-crossing point when the voltage at the line input 110 orthe line input 114 is equal to the voltage at the neutral line input118. The fourth circuit 208 includes two resistors 242 and 244, whichform a voltage divider between the neutral input 118 and ground. A node240 is between the resistor 242 and the resistor 244, and is connectedto the microprocessor 136 at the digital input 163. The resistors 242and 244 are configured to divide the voltage difference between theneutral input 118 and ground to produce at the node 240 a voltage rangethat can be accepted by the microprocessor 136 without the use of an A/Dconverter and can be interpreted as a logic signal. When the line inputs110, 114 are at a zero-crossing point, the voltage at the node 240 iszero, which represents a logic value of zero, and is interpreted by themicroprocessor 136 as a logic value of zero. When the line voltages arenot at a zero-crossing point, the voltage at the node 240 is a positivevalue, which represents a logic value of one, and is interpreted by themicroprocessor 136 as a logic value of one.

The microprocessor 136 is programmed to calculate a value for theline-to-neutral voltage of the line input of positive polarity from theline-to-line voltage measurement and the line-to-neutral voltagemeasurement of the line input of negative polarity in the mannerdescribed above.

In this embodiment, the third circuit 206 and the first circuit 202share at least one component, the resistor 214. The fourth circuit 208and the second circuit 204 also share at least one component, theresistor 222. Sharing components among the circuits can further reducethe number of components on the PCBA and can simplify layout of thecircuitry on the PCBA.

FIG. 3 is a simplified circuit diagram illustrating aspects of thepresent invention, including circuitry for measuring a line-to-linevoltage and a line-to-neutral voltage and determining anotherline-to-neutral voltage. As with FIG. 1A, above, a two pole circuitbreaker 300 includes two line inputs L1 and L2 (110, 114) to receive ACinput voltages (e.g., 120V AC) through the line-powered trip solenoids112, 116, respectively, and the neutral input 118. The full-wave diodebridge 120 and the rectifying diodes 122 and 124 rectify the voltages atthe line inputs 110, 114. The half cycle of positive polarity is inputto the voltage regulator 126, which outputs a regulated voltage.

The circuit breaker 300 includes a first circuit 302 for measuring thevoltage difference between the line inputs 110, 114. The first circuit302 includes a resistor 312 connected to the line input 110, a resistor314, connected in series to the line input 114, and a resistor 316connected to the resistors 312 and 314 and ground. The resistors 312,314, and 316 form voltage dividers between the line inputs 110, 114, andground. A node 310, between the three resistors 312, 314, and 316 isconnected to the microprocessor 136. The resistors 312, 314 and 316 areconfigured to divide the line-to-line voltage to produce at the node 310a range that can be accepted by the microprocessor 136. The voltage atthe node 310 represents the voltage difference between the line inputs110 and 114. The microprocessor 136 includes the A/D converter (notshown), which receives the analog voltage from the node 310 at theanalog input 138 and converts it into a digital representation usable bythe microprocessor 136 by sampling the voltage at the node 310 atregular intervals.

The circuit breaker 300 also includes a second circuit 304 for measuringthe voltage difference between the neutral input 118 and whichever ofthe two line inputs 110, 114 is of a negative polarity. The secondcircuit 304 includes two resistors 322 and 324, which form a voltagedivider between the neutral input 118 and ground. A node 320 is betweenthe resistors 322 and 324. The voltage at the node 320 is a dividedrepresentation of the voltage difference between the voltage at theneutral input 118 and ground. The resistors 322 and 324 are configuredto divide the line-to-neutral voltage to produce at the node 320 a rangethat can be accepted by the microprocessor 136. The voltage at the node320 represents the voltage difference between the neutral input 118 andwhichever of the two line inputs 110, 114 is of a negative polarity. Thenode 320 is connected to the microprocessor 136, which includes the A/Dconverter to receive the analog voltage from node 320 at the analoginput 148 and convert it into a digital representation usable by themicroprocessor 136 by sampling the voltage at the node 320 at regularintervals.

The circuit breaker 300 also includes a third circuit 306 to indicatewhich of the line inputs 110, 114 is at a negative polarity (and whichis at a positive polarity). The third circuit 306 includes two resistors332 and 334 connected between the line input 114 and ground, and whichform a voltage divider. Node 330 is between resistors 332 and 334, andis connected to the microprocessor 136 at the digital input 153. Theresistors 332 and 334 are configured to divide the voltage differencebetween the line input 114 and ground to produce at the node 330 avoltage range that can be accepted by the microprocessor 136 without theuse of an A/D converter and can be interpreted as a logic signal. Thevoltage at the node 330 represents the polarity of the voltage at theline input 114. If the voltage at the line input 114 is of a negativepolarity, the voltage at the node 330 will be zero, representing a logicvalue of zero; if the voltage at the line input 114 is of a positivepolarity, the node 330 will be at a positive potential, representing alogic value of one. The microprocessor 136 interprets a logic value atthe node 330 to indicate that the line input 114 is at a negativepolarity and the line input 110 is at a positive polarity (for logicvalue of zero) or vice versa (for logic value of one).

The circuit breaker 300 may also include a fourth circuit 308 toindicate a zero-crossing point when the voltage at the line input 110 orline input 114 is equal to the voltage at the neutral line 118. Thefourth circuit 308 includes three resistors 342, 344 and 346. Theresistors 342 and 346 form a voltage divider between line input 110 andground, and the resistors 344 and 346 form a voltage divider between theline input 114 and ground. A node 340 is in the center of the resistors342, 344, and 346, and is further connected to the microprocessor 136 atthe digital input 163. The resistors 342, 344, and 346 are configured todivide the voltage differences between the line inputs 110, 114 andground to produce at the node 340 a voltage range that can be acceptedby the microprocessor 136 without the use of an A/D converter and can beinterpreted as a logic signal. When both of the line inputs 110, 114 areat a zero-crossing point, both of the line inputs 110 and 114 will be atthe same potential as ground, and the voltage at the node 340 will bezero. A voltage of zero at the node 340 represents a logic value ofzero, and is interpreted by the microprocessor 136 as a logic value ofzero. When the line voltages are not at a zero-crossing point, thevoltage at the node 340 is a positive value, which represents a logicvalue of one, and is interpreted by the microprocessor 136 as a logicvalue of one. In this embodiment, the fourth circuit 308 is connected tothe two line inputs 110, 114 rather than the neutral input 118. In thecase of a loss or other defect of the neutral input, the microprocessor136 can still detect a zero-crossing, and thus will have a timingreference to use in fault detection algorithms, such as an algorithm todetect a loss of the neutral input.

The microprocessor 136 is programmed to calculate a value for theline-to-neutral voltage of the line input of positive polarity from theline-to-line voltage measurement and the line-to-neutral voltagemeasurement of the line input of negative polarity in the mannerdescribed above.

In this embodiment, each of the first circuit 302, the second circuit304, the third circuit 306, and the fourth circuit 308 is separate fromthe other circuits in that they do not share components with the othercircuits. Keeping the circuits separate can permit tighter measurementtolerances. The fourth circuit 308 is connected between the line inputs110, 114 and ground.

FIG. 4 is a simplified circuit diagram illustrating aspects of thepresent invention, including circuitry for measuring a line-to-linevoltage and a line-to-neutral voltage and determining anotherline-to-neutral voltage. As with FIG. 1A, above, a two pole circuitbreaker 400 includes the two line inputs L1 and L2 (110, 114) to receiveAC input voltages (e.g., 120V AC) through the line-powered tripsolenoids 112, 116, respectively, and the neutral input 118. Thefull-wave diode bridge 120 and the rectifying diodes 122 and 124 rectifythe voltages at the line inputs 110, 114. The half cycle of positivepolarity is input to the voltage regulator 126, which outputs aregulated voltage.

The circuit breaker 400 includes a first circuit 402 for measuring thevoltage difference between the line inputs 110, 114. The first circuit402 includes a resistor 412, connected to line input 110, a resistor414, connected to the line input 114, and a resistor 416 connected tothe resistors 412 and 414 and to ground. The resistors 412, 414, and 416form voltage dividers between the line inputs 110, 114 and ground. Anode 410, between the three resistors 412, 414, and 416 is connected tothe microprocessor 136. The resistors 412, 414, and 416 are configuredto divide the line-to-line voltage to produce at the node 410 a rangethat can be accepted by the microprocessor 136. The voltage at the node410 represents the voltage difference between the line inputs 110 and114. The microprocessor 136 includes the A/D converter (not shown) toreceive the analog voltage from the node 410 at the analog input 138 andconvert it into a digital representation usable by the microprocessor136 by sampling the voltage at the node 410 at regular intervals.

The circuit breaker 400 also includes a second circuit 404 for measuringthe voltage difference between the neutral input 118 and whichever ofthe two line inputs 110, 114 is of negative polarity. The second circuit404 includes two resistors 422 and 424, which form a voltage dividerbetween the neutral input 118 and ground. A node 420 is between theresistors 422 and 424. The voltage at the node 420 is a dividedrepresentation of the voltage difference between the voltage at theneutral input 118 and ground. The resistors 422 and 424 are configuredto divide the line-to-neutral voltage to produce at the node 420 a rangethat can be accepted by the microprocessor 136. The voltage at the node420 represents the voltage difference between the neutral input 118 andwhichever of the two line inputs 110, 114 is of negative polarity. Thenode 420 is connected to the microprocessor 136, which includes the A/Dconverter to receive the analog voltage from the node 420 at the analoginput 148 and convert it into a digital representation usable by themicroprocessor 136 by sampling the voltage at the node 420 at regularintervals.

The circuit breaker 400 also includes a third circuit 406 to indicatewhich of the line inputs 110, 114 is at a negative polarity (and whichis at a positive polarity). The third circuit 406 includes two resistors432 and 434 connected between the line input 114 and ground. Theresistors 432 and 434 form a voltage divider. A node 430 is between theresistors 432 and 434, and is connected to the microprocessor 136 at thedigital input 153. The resistors 432 and 434 are configured to dividethe voltage difference between the line input 114 and ground to produceat the node 430 a voltage range that can be accepted by themicroprocessor 136 without the use of an A/D converter and can beinterpreted as a logic signal. The voltage at the node 430 representsthe polarity of the voltage at the line input 114. If the voltage at theline input 114 is of a negative polarity, the voltage at the node 430will be zero, representing a logic value of zero; if the voltage at theline input 114 is of a positive polarity, the node 430 will be at apositive potential, representing a logic value of one. Themicroprocessor 136 interprets a logic value at the node 430 to indicatethat the line input 114 is at a negative polarity and the line input 110is at a positive polarity (for logic value of zero) or vise versa (forlogic value of one).

The circuit breaker 400 may also include a fourth circuit 408 toindicate a zero-crossing point when the voltage at the line input 110 orthe line input 114 is equal to the voltage at the neutral input 118. Thefourth circuit 408 includes two resistors 442 and 444, which form avoltage divider between the neutral input 118 and ground. A node 440 isbetween the resistors 442 and 444, and is connected to themicroprocessor 136 at the digital input 163. The resistors 442 and 444are configured to divide the voltage difference between the neutralinput 118 and ground and produce at the node 440 a voltage range thatcan be accepted by the microprocessor 136 without the use of an A/Dconverter and interpreted as a logic signal. When the line inputs 110,114 are at a zero-crossing point, the voltage at the node 440 is zero,which represents a logic value of zero, and is interpreted by themicroprocessor 136 as a logic value of zero. When the line voltages arenot at a zero-crossing point, the voltage at the node 440 is a positivevalue, which represents a logic value of one, and is interpreted by themicroprocessor 136 as a logic value of one. In this embodiment, thefourth circuit 408 is connected to the neutral input 118 rather than thetwo line inputs 110, 114. This permits the use of fewer and smallercircuit components, such as smaller resistors, further saving PCBAspace.

The microprocessor 136 is programmed to calculate a value for theline-to-neutral voltage of the line input of positive polarity from theline-to-line voltage measurement and the line-to-neutral voltagemeasurement of the line input of negative polarity in the mannerdescribed above.

In this embodiment, each of the first circuit 402, the second circuit404, the third circuit 406, and the fourth circuit 408 is separate fromthe other circuits in that they do not share components with the othercircuits. Keeping the circuits separate can permit tighter measurementtolerances. The fourth circuit 308 is connected between the neutralinput 118 and ground.

FIG. 5 is a simplified circuit diagram illustrating aspects of thepresent invention, including circuitry for measuring two line-to-neutralvoltages and determining a line-to-line voltage. A two pole circuitbreaker 500 includes two line inputs L1 and L2 (510, 514) to receive ACinput voltages (e.g., 120V AC) through two line-powered trip solenoids512, 516, respectively, and a neutral input 518. The neutral input 518serves as ground. Two rectifying diodes 520 and 522 permit the halfcycles of positive polarity from the line inputs 510 and 514,respectively, while blocking the half cycles of negative polarity. Thehalf cycles of positive polarity are input to a voltage regulator 524,which outputs a regulated voltage. A voltage divider including tworesistors 526 and 528 between the output of the voltage regulator 524and ground produces an analog reference voltage at a node 530. Theanalog reference voltage could also be generated by an active circuit.

The circuit breaker 500 includes a first circuit 531 for measuring thevoltage difference between the line input 510 and the neutral input 518.The first circuit 531 includes two resistors 532 and 534, which form avoltage divider between the line input 510 and the analog reference 530.The resistors 532 and 534 are configured to divide the voltagedifference between the line input 510 and the analog reference 530 toproduce at a node 536 a voltage range that can be accepted by amicroprocessor 538 coupled to the node 536. The analog reference voltageis an offset voltage chosen to ensure that the voltages received by themicroprocessor 538 is an acceptable range (e.g., the analog referencevoltage can be chosen to ensure that the voltages received by themicroprocessor are positive if the microprocessor cannot accept negativevoltages). The first circuit 531 outputs a first analog signal at thenode 536 representing the voltage difference between the line input 510and the neutral input 518. This represents the instantaneous voltage ofthe 120V AC voltage at the line input 510. The node 536 is connected tothe microprocessor 538 at analog input 540. An A/D converter (not shown)at the microprocessor 538 converts the first analog signal to a firstdigital value. The microprocessor 538 samples the first digital value.The microprocessor 538 is programmed to determine a line-to-neutralvoltage measurement from the first digital value, for example bycomparing the first digital value to a set of stored values, or byexecuting a function defining a relationship between the possibledigital values and corresponding line-to-neutral voltage measurements.The microprocessor 538 can store this value for use in calculations.

The circuit breaker 500 also includes a second circuit 541 for measuringthe voltage difference between the line input 514 and the neutral input518. The second circuit 541 includes two resistors 542 and 544, whichform a voltage divider between the line input 514 and the analogreference 530. The resistors 542 and 544 are configured to divide thevoltage difference between the line input 514 and the analog reference530 to produce at a node 546 a voltage range that can be accepted by themicroprocessor 538. The second circuit 541 outputs a second analogsignal at the node 546 representing the voltage difference between theline input 514 and the neutral input 518. This represents theinstantaneous voltage of the 120V AC voltage at the line input 514. Thenode 546 is connected to the microprocessor 538 at analog input 548 TheA/D converter at the microprocessor 538 converts the second analogsignal to a second digital value. The microprocessor 538 samples thesecond digital value. The microprocessor 538 is programmed to determinea line-to-neutral voltage measurement from the second digital value, forexample by comparing the second digital value to a set of stored values,or by executing a function defining a relationship between the possibledigital values and corresponding line-to-neutral voltage measurements.The microprocessor 538 can store this value for use in calculations.

The microprocessor 538 is programmed to calculate a value for theline-to-line voltage between the line inputs 510 and 514 from the twoline-to-neutral voltage measurements. For example, the microprocessor538 can be programmed to add the first digital value to the seconddigital value to calculate a voltage value of the line-to-line voltage.The microprocessor 538 can include an arithmetic logic unit (ALU) toperform such calculations. In this embodiment, a polarity signal is notneeded to determine which voltage measurement corresponds to which lineinput.

The circuit breaker 500 may also include a third circuit 549 to indicatea zero-crossing point when the voltage at the line input 510 or the lineinput 514 is equal to the voltage at the neutral input 518. The thirdcircuit 549 includes three resistors 550, 554 and 558. The resistors 550and 558 form a voltage divider between the line input 510 and theneutral input 518, and the resistors 554 and 558 form a voltage dividerbetween the line input 514 and the neutral input 518. Two diodes 552 and556 prevent current from flowing whichever line input is of a negativepolarity. A node 560 is in the center of the resistors 550, 554, and558, and is further connected to the microprocessor 538 at a digitalinput 561. The resistors 550, 554, and 558, and a diode 562, areconfigured to divide the voltage differences between the line inputs510, 514 and the neutral input 518 to produce at the node 560 a voltagerange that can be accepted by the microprocessor 538 without the use ofan A/D converter and can be interpreted as a logic signal. When both ofthe line inputs 510, 514 are at a zero-crossing point, both of the lineinputs 510 and 514 will be at the same potential as ground, and thevoltage at the node 560 will be zero. A voltage of zero at the node 560represents a logic value of zero, and is interpreted by themicroprocessor 538 as a logic value of zero, which indicates azero-crossing point. When the line voltages are not at a zero-crossingpoint, the voltage at the node 560 is a positive value, which representsa logic value of one, and is interpreted by the microprocessor 538 as alogic value of one, which indicates that the line inputs 510, 514 arenot at a zero crossing point.

FIG. 6 is a simplified circuit diagram illustrating aspects of thepresent invention, including circuitry for measuring two line-to-neutralvoltages and determining a line-to-line voltage. A two pole circuitbreaker 600 includes two line inputs L1 and L2 (610, 614) to receive ACinput voltages (e.g., 120V AC) through two line-powered trip solenoids612, 616, respectively, and a neutral input 618. Two rectifying diodes620 and 622 permit the half cycles of positive polarity from the inputs610 and 614, respectively, while blocking the half cycles of negativepolarity. The half cycles of positive polarity are input to a voltageregulator 624, which outputs a regulated voltage. An inverting regulator626 takes as input the output of the voltage regulator 624 and theneutral input 618, and outputs a negative voltage with respect to thevoltage regulator ground. This negative voltage can be used as themodule ground reference at a node 628.

The circuit breaker 600 includes a first circuit 631 for measuring thevoltage difference between the line input 610 and the neutral input 618.The first circuit 631 includes two resistors 630 and 632, which form avoltage divider between the line input 610 and the neutral input 618.The resistors 630 and 632 are configured to divide the voltagedifference between the line input 610 and the neutral input 618 toproduce at a node 634 a voltage range that can be accepted by amicroprocessor 638 coupled to the node 634. The first circuit 631outputs a first analog signal at the node 634 representing the voltagedifference between the line input 610 and the neutral input 618. Thisrepresents the instantaneous voltage of the 120V AC voltage at the lineinput 610. The node 634 is connected to the microprocessor 638 at ananalog input 640. An A/D converter (not shown) at microprocessor 638converts the first analog signal to a first digital value. Themicroprocessor 638 samples the first digital value. The microprocessor638 is programmed to determine a line-to-neutral voltage measurementfrom the first digital value, for example by comparing the first digitalvalue to a set of stored values, or by executing a function defining arelationship between the possible digital values and correspondingline-to-neutral voltage measurements. The microprocessor 638 can storethis value for use in calculations.

The circuit breaker 600 also includes a second circuit 641 for measuringthe voltage difference between the line input 614 and the neutral input618. The second circuit 641 includes two resistors 642 and 644, whichform a voltage divider between the line input 614 and the neutral input618. The resistors 642 and 644 are configured to divide the voltagedifference between the line input 614 and the neutral input 618 toproduce at a node 646 a voltage range that can be accepted by themicroprocessor 638. The second circuit 641 outputs a second analogsignal at the node 646 representing the voltage difference between theline input 614 and the neutral input 618. This represents theinstantaneous voltage of the 120V AC voltage at the line input 614. Thenode 646 is connected to the microprocessor 638 at an analog input 648.The A/D converter at microprocessor 638 converts the second analogsignal to a second digital value. The microprocessor 638 samples thesecond digital value. The microprocessor 638 is programmed to determinea line-to-neutral voltage measurement from the second digital value, forexample by comparing the second digital value to a set of stored values,or by executing a function defining a relationship between the possibledigital values and corresponding line-to-neutral voltage measurements.The microprocessor 638 can store this value for use in calculations.

The microprocessor 638 is programmed to calculate a value for theline-to-line voltage between the line inputs 610 and 614 from the twoline-to-neutral voltage measurements. For example, the microprocessor638 can be programmed to add the first digital value to the seconddigital value to calculate a calculated voltage value of theline-to-line voltage. The microprocessor 638 can include an arithmeticlogic unit (ALU) to perform such calculations. In this embodiment, apolarity signal is not needed to determine which voltage measurementcorresponds to which line input.

The circuit breaker 600 may also include a third circuit 649 to indicatea zero-crossing point when the voltage at line the input 610 or the lineinput 614 is equal to the voltage at the neutral input 618. The thirdcircuit 649 includes three resistors 650, 654 and 658. The resistors 650and 658 form a voltage divider between the line input 610 and ground628, and the resistors 654 and 658 form a voltage divider between theline input 614 and ground 628. Two diodes 652 and 656 prevent currentfrom flowing whichever line input is of a negative polarity. A node 660is in the center of the resistors 650, 654, and 658, and is furtherconnected to the microprocessor 638 at a digital input 661. Theresistors 650, 654, and 658 are configured to divide the voltagedifferences between the line inputs 610, 614 and ground 628 to produceat the node 660 a voltage range that can be accepted by themicroprocessor 638 without the use of an A/D converter and can beinterpreted as a logic signal. When both of the line inputs 610, 614 arepassing through a zero-crossing point, both of the line inputs 610 and614 will be at the same potential as the neutral input 618, and thevoltage at the node 660 will be zero. A voltage of zero at the node 660represents a logic value of zero, and is interpreted by themicroprocessor 638 as a logic value of zero, which indicates azero-crossing point. When the line voltages are not at a zero-crossingpoint, the voltage at the node 660 is a positive value, which representsa logic value of one, and is interpreted by the microprocessor 638 as alogic value of one, which indicates that the line inputs 610, 614 arenot at a zero crossing point.

FIG. 7 is a simplified circuit diagram illustrating aspects of thepresent invention, including circuitry for measuring a line-to-linevoltage and a line-to-neutral voltage and determining anotherline-to-neutral voltage, without a circuit to determine polarity. A twopole circuit breaker 700 includes two line inputs L1 and L2 (710, 714)to receive AC input voltages (e.g., 120V AC) through two line-poweredtrip solenoids 712, 716, respectively, and a neutral input 718. Innormal operation, diode 720 half wave rectifies the AC line voltages; ifthere is a loss of phase or other defect on line input 710, diode 722half wave rectifies the line voltage at line input 714. An invertingregulator 726 takes as input the output of the voltage regulator 724 andthe line input 714 (which serves as an analog reference), and outputs aground at a node 728.

The circuit breaker 700 includes a first circuit 730 for measuring theline-to-line voltage difference between the line input 710 and the lineinput 714. The first circuit 730 includes two resistors 732 and 734,which form a voltage divider between the line input 710 and the lineinput 714. The resistors 732 and 734 are configured to divide thevoltage difference between the line input 710 and the line input 714 toproduce at a node 736 a voltage range that can be accepted by amicroprocessor 738 coupled to the node 736. The first circuit 730outputs a first analog signal at the node 736 representing theline-to-line voltage difference. This represents the instantaneousvoltage of the 240V AC voltage between the line inputs 710 and 714. Thenode 736 is connected to the microprocessor 738 at an analog input 740.An A/D converter (not shown) at the microprocessor 738 converts thefirst analog signal to a first digital value. The microprocessor 738samples the first digital value. The microprocessor 738 is programmed todetermine a line-to-line voltage measurement from the first digitalvalue, for example by comparing the first digital value to a set ofstored values, or by executing a function defining a relationshipbetween the possible digital values and corresponding line-to-linevoltage measurements. The microprocessor 738 can store this value foruse in calculations.

The circuit breaker 700 also includes a second circuit 742 for measuringthe voltage difference between the line input 714 and the neutral input718. The second circuit 742 includes two resistors 744 and 746, whichform a voltage divider between the line input 714 and the neutral input718. The resistors 744 and 746 are configured to divide the voltagedifference between the line input 714 and the neutral input 718 toproduce at a node 748 a voltage range that can be accepted by themicroprocessor 738. The second circuit 742 outputs a second analogsignal at the node 748 representing the voltage difference between theline input 714 and the neutral input 718. This represents theinstantaneous voltage of the 120V AC voltage at the line input 714. Thenode 748 is connected to the microprocessor 738 at an analog input 750.The A/D converter at the microprocessor 738 converts the second analogsignal to a second digital value. The microprocessor 738 samples thesecond digital value. The microprocessor 738 is programmed to determinea line-to-neutral voltage measurement from the second digital value, forexample by comparing the second digital value to a set of stored values,or by executing a function defining a relationship between the possibledigital values and corresponding line-to-neutral voltage measurements.The microprocessor 738 can store this value for use in calculations.

The microprocessor 738 is programmed to calculate a value for theline-to-neutral voltage between the line input 710 and the neutral input718 from the line-to-line measurement and the line-to-neutralmeasurement between the line input 714 and the neutral input 718. Forexample, the microprocessor 738 can be programmed to subtract the seconddigital value from the first digital value to calculate a calculatedvoltage value of the line-to-neutral voltage between the line input 710and the neutral input 718. The microprocessor 738 can include anarithmetic logic unit (ALU) to perform such calculations. In thisembodiment, a polarity signal is not needed to determine which voltagemeasurement corresponds to which line input.

The circuit breaker 700 may also include a third circuit 752 to indicatea zero-crossing point when the voltage at the line input 710 or the lineinput 714 is equal to the voltage at the neutral input 718. The thirdcircuit 752 includes a resistor 754 and diodes 758 and 760, configuredto keep the voltage at a node 756 in a range that can be accepted by themicroprocessor 738 without the use of an A/D converter and can beinterpreted as a logic signal. The node 756 is coupled to themicroprocessor 738 at a digital input 757. The neutral input 718 is at adifferent potential than ground 728, and the relationship changes as theline inputs 710, 714 switch polarity. When both of the line inputs 710,714 transition from one polarity to the other, the signal at the node756 changes states (e.g., from zero voltage to a positive voltage, orvice versa). A voltage of zero at the node 756 represents a logic valueof zero, and is interpreted by the microprocessor 738 as a logic valueof zero. Likewise, a positive voltage at the node 756 represents a logicvalue of one, and is interpreted by the microprocessor 738 as a logicvalue of one. The microprocessor 738 can be programmed to determine thata transition from logic zero to logic one, or a transition from logicone to logic zero, indicates a zero crossing point.

Detected line voltage values can be used by a microprocessor to identifyan improper voltage value and initiate an appropriate response. Impropervoltage values can include overvoltage conditions, undervoltageconditions, AC line voltage frequency that is too high or too low, linevoltage waveform that is not sinusoidal, single or multiple stepfunction approximated sine waves, a loss of phase, or loss of panelneutral. Responses initiated by the microprocessor can include trippingthe circuit breaker (breaking the circuit), and can also includegenerating a signal, such as a visual or audible signal or communicationof a signal to an external device.

With reference to FIG. 8, there is shown a method 800 of tripping acircuit breaker in response to an overvoltage condition. An overvoltagecondition can occur in a two pole circuit breaker (such as described forFIGS. 1A and 2-4 above), for example, when the connection of the neutralline input (e.g., FIG. 1A, neutral input 118) is lost. In such a case,the effective neutral voltage will drift according to the relativeimpedances of the loads coupled to the line inputs (e.g., FIG. 1A, lineinputs 110, 114), with a higher line-to-neutral voltage resulting on theline with highest impedance. Similarly, in a system that uses aplurality of one-pole circuit breakers, a loss of panel neutral (neutralline connected to the circuit breaker panel) can result in some or allof the one-pole circuit breakers becoming unbalanced, based on therespective impedances of their loads.

The method 800 can be performed, for example, with software executing ona microprocessor. The method includes accumulating a summation, orintegration, of voltage values over time to generate a V_(area) value.The V_(area) value is initially set to zero (808). A line-to-neutralvoltage V(n) is sampled by a microprocessor at regular intervals (810),for example 32 samples for each half cycle of the line-to-neutralvoltage (approximately 8.3 ms), where V(n) is the sampled voltage valueat a particular interval n. For a two-pole circuit breaker, themicroprocessor determines which of the poles is being sampled. Asdescribed above, for the two-pole circuit breakers described in FIGS. 1Aand 2-4, the microprocessor 136 samples the line-to-line voltage betweenthe line inputs 110, 114, and samples the line-to-neutral voltagebetween the neutral input 118 and whichever of the line inputs 110, 114is at negative polarity. The microprocessor 136 determines, using thepolarity signal, which of the line-to-neutral voltages it is sampling,and calculates the other line-to-neutral voltage as described above. Ina one-pole circuit breaker, the line-to-neutral voltage is a voltagemeasured between the single line input and a neutral input.

The microprocessor can analyze a set of samples collected during asampling period. For example, the microprocessor can be configured torecognize a zero-crossing point as approximately the beginning of theset of samples and a subsequent zero-crossing point as approximately theend of the set of samples. The microprocessor can continuously samplethe line-to-neutral voltage, with discrete sets of samples delineated byzero-crossing points. For the two-pole circuit breakers described abovein relation to FIGS. 1A and 2-4, a zero-crossing point can be determinedby sampling the output of the respective fourth circuits. Likewise, forthe two-pole circuit breakers described in relation to FIGS. 5-7 above,a zero-crossing point can be determined by sampling the output of therespective third circuits. A one-pole circuit breaker can also includesimilar circuitry configured to output to a microprocessor a signalindicative of a zero-crossing point, for example by determining when theline voltage is equal to the neutral voltage.

The sampled voltage values V(n) are accumulated by the microprocessor togenerate the V_(area) value (812). The microprocessor can detect asubsequent zero-crossing point (814) and determine a final V_(area)value at approximately the subsequent zero-crossing point. The initialvalue of V_(area) at the first sample is V(0), and for each sample V(n)during the half cycle, V_(area) is incremented by V(n). Thus, after ahalf cycle, V_(area) is equal to the sum of the approximately 32 samplesof the line-to-neutral voltage during that half cycle. V_(area) can beconsidered an estimate of the amount of energy delivered (during halfcycles where the voltage exceeds a threshold) to components downstream(e.g., the load connected to the circuit breaker) from the circuitbreaker over the sampled period of time (here, one half cycle of theline-to-neutral voltage). Alternatively, V_(area) can be computed byintegrating the line-to-neutral voltage over the half cycle period.

After the microprocessor detects the zero-crossing point indicating theend of the set of samples, V_(area) can be compared against thethreshold value (816). The threshold value represents a minimum valuethat can be considered an overvoltage condition for the sampled periodof time. For example, the threshold value can be set to be a value thatrepresents the accumulation of a set of 140V RMS samples over one halfcycle of the line-to-neutral voltage.

The threshold value can be chosen by estimating the amount ofovervoltage time components downstream from the circuit breaker canwithstand before potentially being damaged. For example, the ITI (CBEMA)Curve illustrates an estimate by the Information Technology IndustryCouncil (“ITI”) of AC voltages that most information technologyequipment can tolerate for a corresponding period of time. See ITI(CBEMA) Curve Application Note published by Information TechnologyIndustry Council (“ITI”), 1250 Eye Street NW, Suite 200, Washington,D.C. 20005 (available on the ITIC website). FIG. 9 shows the ITI (CBEMA)Curve 910. The ITI (CBEMA) Curve associates RMS AC voltage on the X-axis912 with time (in both seconds and cycles) on the Y-axis 914 (note thatthe curve in the ITI (CBEMA) Curve Application Note depicts the curve ina graph with a percentage of nominal RMS AC voltage on the Y-axis andtime on the X-axis. This information has been reformatted into curve 910to allow easier comparison to other curves discussed below. Theinformation in the curve depicted in the ITI (CBEMA) Curve ApplicationNote is the same as depicted in FIG. 9, curve 910). Voltage and timecombinations above the curve exceed the ITI's estimates for thetolerance of information technology equipment. For example, an RMSvoltage of 140V for a duration of 20 ms would be above the ITI (CBEMA)Curve, and thus would exceed the ITI's tolerance estimate.

If V_(area) exceeds the threshold value, a trip curve time value, forexample a maximum time delay T_(max), is computed for the value ofV_(area) according to a function (818). T_(max) is an estimate of themaximum amount of time an overvoltage of a given value will be toleratedbefore action (e.g., tripping the circuit breaker) is taken. Thefunction maps voltage values to corresponding time values. The functioncan be a trip curve function. For example, the trip curve function cancorrespond to the ITI (CBEMA) Curve, or a portion of the curve, suchthat the trip curve function will output a T_(max) value correspondingto a voltage value on the ITI (CBEMA) Curve. For example, if V_(area)corresponds to a voltage of 200V, the function would output a value ofapproximately 1 ms. The trip curve function or functions (for example, aseparate function can be implemented for each region of the ITI (CBEMA)Curve) can be stored in a memory in the microprocessor. Either V_(area)can be scaled to correspond to RMS voltage values on the trip curve, orthe RMS values of the trip curve function can be scaled to correspond toV_(area) values.

A trip curve function (or functions) can also be derived by measuringthe behavior of a circuit component, for example a metal oxide varistor(“MOV”), used in the circuit breaker. FIG. 9 depicts a trip curve 916derived from a MOV energy rating curve that can be used with the circuitbreakers described above for FIGS. 1A, and 2-4. The trip curve 910associates voltage values on a Y-axis 912 with corresponding time valueson an X-axis 914. A trip curve derived from, for example, a MOV 125 usedin the circuit breaker 100 of FIG. 1A can provide an estimate of theamount of overvoltage that the circuit breaker itself can tolerate. Ifthe function corresponds to trip curve 916, more energy may be permittedto flow downstream before action is taken than if the functioncorresponds to the ITI (CBEMA) Curve 910.

A trip curve can be chosen to be between the ITI (CBEMA) Curve 910 andthe MOV trip curve 916. For example, a trip curve 918 is chosen to bebetween the ITI (CBEMA) Curve 910 and the MOV trip curve 916. Empiricaltesting can be used to confirm that common components (e.g., lightbulbs) burn out at exposure times higher than those on trip curve 918for a given overvoltage value. The equation for the trip curve 918 is:T _(max)=97.5 seconds−V _(rms)*(0.5 seconds/Volts)   (Equation 1)The trip curve function mapping voltage values to corresponding timevalues can include Equation 1. Using Equation 1, V_(rms) is compared tovalues representing the accumulation of samples of voltages at values ona Y-axis 1012 for time periods of corresponding lengths on an X-axis1014.

The trip curve of Equation 1 can be scaled for convenient use by themicroprocessor. For example, time can be represented in units ofhalf-cycles rather than seconds:120 T _(max)=120(97.5 seconds−(0.5 seconds/Volts RMS)   (Equation 2)Equation 2 can be rewritten as:T _(hc)=120(97.5 seconds−(0.5 seconds/Volts RMS)   (Equation 3)where t_(hc)=120 t_(max). V_(area) can be used as an approximation ofthe RMS voltage over a half cycle, and can be chosen to be easier toprocess with the microprocessor. V_(area) can be represented as A*V_(rms), where V_(rms) is a corresponding approximate RMS voltagevalue, and A is in units of bits/V_(rms). Equation 3, then, can bewritten in terms of V_(area):T _(hc)=11700−(60/A)*V _(area)   (Equation 4)A can be chosen to conveniently represent the function in themicroprocessor, for example A=74.75. Equation 4, then, can beimplemented by the microprocessor by:T _(hc)=11700−(13150/2¹⁴)*V _(area)   (Equation 5)where (13150/2¹⁴) is approximately (60/74.75).

The microprocessor uses T_(max) (or a scaled value such as T_(hc)corresponding to T_(max)) to increment a Count value by an estimate ofthe amount of excess energy delivered to the load during the half-cycle(820). The Count value is a 16-bit number that represents an accumulatedamount of overvoltage time that has been delivered to the load overtime. A person of ordinary skill in the art will recognize that othernumbers of bits (e.g., 32 bits) may be appropriate, depending on themicroprocessor chosen. The count value can be incremented according tothe following equation, which increments the Count value by a fractionof a Count_(max) value, the fraction being determined by T_(max):Count=Count+Count_(max) /T _(max)   (Equation 6)The initial value of the Count value is zero. Although the Varea valueis reset to zero before the first sample of every half cycle, the Countvalue is not reset, and is carried over from one sampling period to thenext. Thus, over the course of a plurality of half cycles, the Countvalue represents an accumulation of energy delivered to downstreamcomponents over that period of time. For example, if the line-to-neutralvoltage is above the threshold for several half cycles, the Count valuewill continue to increment, representing an increasing amount ofovervoltage energy delivered to downstream components over that periodof time. Thus, although one half cycle of a particular overvoltage valuemay not cause the circuit breaker to trip, a longer period of time atthat overvoltage level might.

The Count_(max) value represents a maximum amount of overvoltage timeabove which the microprocessor initiates an action The Count_(max) valueis a 16-bit number chosen to achieve the highest resolution whenincrementing the Count value. For example, Count_(max) can be chosen tobe 65,535. Again, different numbers of bits can be used, depending onthe microprocessor selected.

The Count value for the current half-cycle is compared to theCount_(max) value (822). If the Count value is greater than or equal tothe Count_(max) value, the microprocessor initiates an appropriateaction, such as causing the circuit breaker to trip (824), or giving avisual or audible indication. For example, referring to FIG. 1A, themicroprocessor 136 conventionally switches an output pin (not shown)that is coupled to a silicon controlled rectifier (“SCR,” not shown)from low to high, causing the SCR to conduct, which in turn energizesthe trip solenoid (112 or 116) to break the circuit. A trip solenoid ina one-pole circuit breaker can be tripped similarly.

After the Count value is compared to the Count_(max) value, the test forthe current half cycle of the line-to-neutral voltage is complete (826).However, the microprocessor can continue to sample the line-to-neutralvoltage during subsequent half-cycles, and the V_(area) values for thosehalf cycles can be tested similarly. As described above, the Count valueis carried over from one half cycle to the next, and represents arunning estimate of energy delivered to downstream components. Thus,subsequent tests of V_(area) may continue to increase the Count valueuntil the circuit breaker trips.

Returning to step 816, if the V_(area) value does not exceed thethreshold value, then the line-to-neutral voltage is less than theminimum value that can be considered an overvoltage condition for thesampled period of time. If the Count value is greater than zero (828),the Count value is decayed, i.e., reduced (830). For example, the Countvalue can be decayed by a predetermined time constant, τ=46 seconds. Inthis example, the Count value would be decayed by 32,762/2¹⁵ for thehalf cycle. As explained above, the Count value keeps a running estimateof the amount of energy delivered to downstream components. Thus, duringhalf cycles where V_(area) is greater than the threshold value, theCount value is incremented, increasing the likelihood that the circuitbreaker will trip; and during half cycles where V_(area) is less thanthe threshold value, the Count value is reduced, lessening thelikelihood that the circuit breaker will trip.

Note that, since the V_(area) value is not compared to the thresholdvalue until a half cycle has elapsed, the circuit breaker will not betripped until at least a half cycle has elapsed. Tripping the circuitbreaker too soon can be considered a nuisance to the user of the circuitbreaker. V_(area) can be compared to the threshold value sooner (e.g.,at approximate a quarter cycle) if greater sensitivity is desired.

Other improper voltage conditions can be detected. For example, anundervoltage condition can be detected for a line-to-neutral voltage.For example, a two-pole circuit breaker (such as described for FIGS. 1Aand 2-7 above) can be configured to trip if the line-to-line voltagesags below a certain minimum value and the difference between therespective line-to-neutral voltages is above a certain maximum value.The minimum value can be the minimum normal operating voltage for aSquare D QO® or HOMELINE® miniature circuit breaker. For example, thecircuit breaker can trip when, for a time period of approximately 66.7ms (8 consecutive half cycles of a line voltage), the line-to-linevoltage is less than 85% of the nominal voltage and the followingequation is satisfied:|(line 1-to-neutral voltage)−(line 2-to-neutral voltage)|>50V.  (Equation 7)In the example of FIG. 1A, the line 1-to-neutral voltage is the voltagedifference between the line input 110 and the neutral input 118; theline 2-to-neutral voltage is the voltage difference between the lineinput 114 and the neutral input 118.

What has been shown is that a line-to-line voltage and twoline-to-neutral voltages can be measured using only two of a limitednumber of analog inputs of a microprocessor. Also, the number of circuitcomponents and high-voltage traces needed to measure a line-to-linevoltage and two line-to-neutral voltages can be reduced, saving space ona PCBA.

What has also been shown is that an improper line-to-neutral voltage canbe detected by monitoring the line-to-neutral voltage and comparing itto a function such as a trip curve. Thus, components downstream from acircuit breaker, as well as the circuit breaker itself, can be protectedfrom prolonged exposure to improper voltages, which can lead tocomponent failure. Specifically, by detecting an overvoltage conditionand tripping the circuit breaker upon detection of the overvoltagecondition, the circuit breaker and downstream components can beprotected from overheating due to the overvoltage condition.

While particular aspects, embodiments, and applications of the presentinvention have been illustrated and described, it is to be understoodthat the invention is not limited to the precise construction andcompositions disclosed herein and that various modifications, changes,and variations may be apparent from the foregoing descriptions withoutdeparting from the spirit and scope of the invention as defined in theappended claims.

What is claimed is:
 1. A method of tripping a circuit breaker during animproper line-to-neutral voltage condition comprising: sampling analternating current (AC) line-to-neutral voltage (“AC line voltage”) atregular intervals during a first time period to generate a plurality ofAC line voltage samples; summing each sample of the set of AC linevoltage samples to generate a voltage area value; determining via acontroller whether the voltage area value exceeds a threshold; and inresponse to the voltage area value exceeding the threshold, adding anamount proportional to the voltage area value and determined as afunction of the voltage area value to a count value representing excessenergy delivered to a load, and causing a circuit breaker to trip inresponse to the count value equaling or exceeding a maximum count value.2. The method of claim 1, further comprising: detecting a zero crossingpoint when the AC line voltage is equal to a neutral voltage; andwherein the first time period ends approximately when the zero crossingpoint is detected.
 3. The method of claim 1, wherein adding to the countvalue an amount determined as a function of the voltage area valuecomprises: calculating a trip curve time value corresponding to thevoltage area value; and incrementing the count value by an amount equalto the maximum count value divided by the time value.
 4. The method ofclaim 3, wherein the trip curve time value corresponding to a voltagearea value is selected to be approximately 97.5 seconds−RMS voltage*(0.5seconds/Volts), wherein the voltage area value is an approximation ofRMS voltage.
 5. The method of claim 3, wherein the trip curve time valuecorresponding to a voltage area value is defined by a functioncharacterized by the ITI-CBEMA RMS Voltage Curve.
 6. The method of claim1, further comprising: if voltage area value does not exceed thethreshold, decaying the count value by a predetermined amount.
 7. Themethod of claim 1, wherein the summing includes an integral function. 8.A circuit breaker for breaking a circuit during an improperline-to-neutral voltage condition comprising: a first circuit configuredto receive an alternating current (AC) line-to-neutral voltage (“AC linevoltage”) and generate a signal indicative of the AC line voltage; and acontroller coupled to the first circuit configured to: sample the ACline voltage at regular intervals during a first time period to generatea plurality of AC line voltage samples; sum each sample of the set of ACline voltage samples to generate a voltage area value; determine whetherthe voltage area value exceeds a threshold; and in response to thevoltage area value exceeding the threshold, add an amount proportionalto the voltage area value and determined as a function of the voltagearea value to a count representing excess energy delivered to a load,and cause a circuit breaker to trip in response to the count valueequaling or exceeding a maximum count value.
 9. The circuit breaker ofclaim 8, wherein the controller is configured to: calculate a trip curvetime value corresponding to the voltage area value; and increment thecount value by an amount equal to the maximum count value divided by thetime value.
 10. The circuit breaker of claim 9, wherein the trip curvetime value corresponding to a voltage area value is selected to beapproximately 97.5 seconds−RMS voltage*(0.5 seconds/Volts), wherein thevoltage area value is an approximation of RMS voltage.
 11. The circuitbreaker of claim 8, further comprising: a second circuit coupled to thecontroller, a first AC line input, and a second AC line input configuredto output a line-to-line signal representing a line-to-line voltage; anda third circuit coupled to the controller configured to output apolarity signal representing an identification of the AC line input, ofthe first AC line input and second AC line input, of negative polarity;wherein the controller is configured to identify the AC line voltagewith the AC line input of negative polarity.
 12. The circuit breaker ofclaim 8, further comprising: a zero-crossing detection circuit coupledto the controller configured to output to the controller a zero-crossingsignal indicating that the AC line voltage is equal to a neutralvoltage; wherein the first time period ends approximately when the zerocrossing point is detected.
 13. The circuit breaker of claim 8, whereinthe controller is configured to decay the count value by a predeterminedamount if voltage area value does not exceed the threshold.
 14. Thecircuit breaker of claim 8, wherein the controller is configured to sumeach sample of the set of AC line voltage samples using an integralfunction.
 15. In a two-pole circuit breaker, a method of breaking acircuit during an anomalous line-to-neutral voltage condition, themethod comprising: receiving a first alternating current (AC)line-to-neutral voltage (“AC line voltage”); identifying the polarity ofthe first AC line voltage; receiving a second AC line voltage 180degrees out of phase from the first AC line voltage; sampling at a firstanalog input of a controller a line-to-line voltage between the first ACline voltage and the second AC line voltage; sampling at a second analoginput of the controller a first line-to-neutral voltage between thefirst AC line voltage and a neutral voltage when the polarity of thefirst AC line voltage is identified as positive; and calculating at thecontroller a second line-to-neutral voltage between the second AC linevoltage and the neutral voltage using the line-to-line voltage and thefirst line to neutral voltage; summing a plurality of samples of thefirst AC line voltage to generate a voltage area value; and if thevoltage area value indicates that the first AC line voltage is ananomalous voltage, causing a circuit breaker to trip.
 16. The method ofclaim 15, wherein the anomalous voltage is an undervoltage.
 17. Themethod of claim 15, wherein the anomalous voltage is an overvoltage. 18.The method of claim 17, further comprising comparing the first AC linevoltage to a trip curve function.